Merge branch 'ipv6-fix-EFAULT-on-sendto-with-icmpv6-and-hdrincl'

Olivier Matz says:

====================
ipv6: fix EFAULT on sendto with icmpv6 and hdrincl

The following code returns EFAULT (Bad address):

  s = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
  setsockopt(s, SOL_IPV6, IPV6_HDRINCL, 1);
  sendto(ipv6_icmp6_packet, addr);   /* returns -1, errno = EFAULT */

The problem is fixed in the second patch. The first one aligns the
code to ipv4, to avoid a race condition in the second patch.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/raw.c

@@ -783,6 +783,7 @@ static int rawv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	struct flowi6 fl6;
 	struct ipcm6_cookie ipc6;
 	int addr_len = msg->msg_namelen;
+	int hdrincl;
 	u16 proto;
 	int err;
 
@@ -796,6 +797,13 @@ static int rawv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	if (msg->msg_flags & MSG_OOB)
 		return -EOPNOTSUPP;
 
+	/* hdrincl should be READ_ONCE(inet->hdrincl)
+	 * but READ_ONCE() doesn't work with bit fields.
+	 * Doing this indirectly yields the same result.
+	 */
+	hdrincl = inet->hdrincl;
+	hdrincl = READ_ONCE(hdrincl);
+
 	/*
 	 *	Get and verify the address.
 	 */
@@ -887,11 +895,14 @@ static int rawv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	opt = ipv6_fixup_options(&opt_space, opt);
 
 	fl6.flowi6_proto = proto;
+
+	if (!hdrincl) {
 		rfv.msg = msg;
 		rfv.hlen = 0;
 		err = rawv6_probe_proto_opt(&rfv, &fl6);
 		if (err)
 			goto out;
+	}
 
 	if (!ipv6_addr_any(daddr))
 		fl6.daddr = *daddr;
@@ -908,7 +919,7 @@ static int rawv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		fl6.flowi6_oif = np->ucast_oif;
 	security_sk_classify_flow(sk, flowi6_to_flowi(&fl6));
 
-	if (inet->hdrincl)
+	if (hdrincl)
 		fl6.flowi6_flags |= FLOWI_FLAG_KNOWN_NH;
 
 	if (ipc6.tclass < 0)
@@ -931,7 +942,7 @@ static int rawv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		goto do_confirm;
 
 back_from_confirm:
-	if (inet->hdrincl)
+	if (hdrincl)
 		err = rawv6_send_hdrinc(sk, msg, len, &fl6, &dst,
 					msg->msg_flags, &ipc6.sockc);
 	else {